Trilaminate film for forming sideweld bags

Abstract

Sideweld bags having strong sidewelds can be made from a trilaminate film comprising a core layer of an ethylene-propylene block copolymer sandwiched between skin layers of polypropylene or an ethylene-propylene random copolymer.

We claim: 
     
       1. A trilaminate film made by coextrusion comprising a core layer sandwiched between skin layers, the core layer having a thickness of from about 30 to 90 percent of the thickness of the film and consisting essentially of an ethylene-propylene block copolymer and up to 40 percent of the weight of the film of recycled trilaminate trim consisting of said core layer and said skin layers, the block copolymer being the homogeneous product resulting from the sequential polymerization of (1) propylene and (2) a mixture of propylene and ethylene in the presence of a stereospecific polymerization catalyst, with the ethylene content of the block copolymer being from about five to ten mole percent, each skin layer having a thickness of from about 5 to about 35 percent of the thickness of the film and consisting essentially of polypropylene or an ethylene-propylene random copolymer having an ethylene content up to about four mole percent. 
     
     
       2. The film of claim 1 having a thickness of from about one to about two mils. 
     
     
       3. The film of claim 1 wherein the core layer has a thickness of from about 50 to 70 percent of the thickness of the film and each skin layer has a thickness of from about 15 to 25 percent of the thickness of the film. 
     
     
       4. The film of claim 3 wherein the thicknesses of the skin layers are the same. 
     
     
       5. The film of claim 4 wherein the skin layers consist essentially of polypropylene. 
     
     
       6. The film of claim 4 wherein the skin layers consist essentially of an ethylene-propylene random copolymer having an ethylene content up to four mole percent. 
     
     
       7. The film of claim 1 in the form of a sideweld bag.